Disproportionation Equilibrium of a μ‐Oxodiiron(III) Complex Giving Rise to C−H Activation Reactivity: Structural Snapshot of a Unique Oxoiron(IV) Adduct. (3rd July 2019)

• Record Type: Journal Article
• Authors: Cordes (née Kupper), Claudia; Morganti, Massimiliano; Klawitter, Iris; Schremmer, Claudia; Dechert, Sebastian; Meyer, Franc
• Is Part Of: Angewandte Chemie. Volume 131:Number 32(2019)
• Page Start: 10971
• Page End: 10974
• Publication Date: 2019-07-03
• Subjects: C-H-Aktivierung -- Eisen -- Eisen-Oxo-Komplexe -- N-Heterocyclische Carbene -- Reaktionskinetik; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201900683
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: μ‐Oxodiiron(III) species are air‐stable and unreactive products of autoxidation processes of monomeric heme and non‐heme iron(II) complexes. Now, the organometallic [(L NHC )Fe III ‐(μ‐O)‐Fe III (L NHC )] 4+ complex 1 (L NHC is a macrocyclic tetracarbene) is shown to be reactive in C−H activation without addition of further oxidants. Studying the oxidation of dihydroanthracene, it was found that 1 thermally disproportionates in MeCN solution into its oxoiron(IV) (2 ) and iron(II) components; the former is the active species in the observed oxidation processes. Possible cleavage scenarios for 1 are shown by scrambling experiments and structural characterization of an unprecedented adduct of 1 and oxoiron(IV) complex 2 . Kinetic analysis gave an equilibrium constant for the disproportionation of 1, which is very small ( K eq =7.5±2.5×10 −8 m ). Increasing K eq might by a useful strategy for circumventing the formation of dead‐end μ‐oxodiiron(III) products during Fe‐based homogeneous oxidation catalysis. Abstract : Scrambling‐Experimente und kinetische Analysen weisen auf eine thermische Disproportionierung eines durch Tetracarbenliganden koordinierten μ‐Oxodieisen(III)‐Komplexes hin, was die C‐H‐Aktivierung von Substraten durch das resultierende Oxoeisen(IV)‐Intermediat ermöglicht. Die strukturelle Charakterisierung des Addukts zwischen der Oxoeisen(IV)‐ und μ‐Oxodieisen(III)‐Spezies liefert eine Momentaufnahme des Scrambling‐Prozesses.